1. Field of the Invention
This invention relates to an apparatus to control a paper conveyance device which is optionally connected to an image forming device and an image processing apparatus which uses the paper conveyance control apparatus.
The term paper conveyance device refers to paper ejecting or processing device such as a paper feeding device, paper ejecting device, stacker, or furnisher of the sheet on which the image is to be formed.
2. Related Background Art
Conventionally, in the image forming device using the electronic photographic system, the whole image forming device is controlled collectively as equipped with the image forming control device to control the whole electronic photographic process including paper feeding and ejecting processing. Additionally, if the paper feeding and ejecting devices are optionally added to the conventional device, those additional devices are connected to the image forming control device on a one-to-one basis.
Also, the commands to move the paper feeding and ejecting devices and the status information of those devices are given via the image forming control device.
In recent years, however, it has been requested to make common the image forming part which is the heart of the image forming device and recombine the paper feeding and ejecting devices to be attached around it according to need. Thus, it is necessary in the conventional configuration to replace the image forming control device itself or to incorporate the control programs and the interfaces of all the connectable paper feeding and ejecting devices into the image forming control device beforehand.
Additionally, the CPU of the image forming control device bears a heavy burden since the commands and statuses of the paper feeding and ejecting devices are given via the image forming control device. Recently there has been a request to display the movements and statuses of the image forming device in as detailed a manner as possible on a real-time basis to the user to promote user-friendliness. It has therefore become necessary to send every one of the status signals of the paper feeding and ejecting devices as well to the host computer side.
In such a case, the image forming control device existing between them incurs such problems as the communication speed becoming low or an insufficient amount of information being provided to the user. Also, to solve these problems, an expensive CPU must be used in the image forming control device or the image forming control device, must have a large-capacity random access memory to store the status information of the paper feeding and ejecting devices.
In attaching a paper ejecting device like the stacker to the image forming device like the page printer of the electronic photographic system, there are some types of such paper ejecting devices which have a job offsetting function to sort the paper ejecting output per series of jobs.
In the conventional example above, however, it becomes impossible to sort a job if another job is printed by interruption during sorting of the first job since it is divided. Therefore, interrupted print cannot be used.
It is impossible to use the image forming device and the optional unit as combined if either one of them is changed. This is because of the difference in the paper conveying speed and path of each image forming device model and that in the paper conveying speed and path and paper processing time of the optional unit, e.g., the stapling processing and paper folding processing time of the furnisher and the sorting time of the sorter.
While it is not in principle impossible to program all such conceivable information in the memory of the CPU of the image forming control device memory beforehand, the optional unit is not always attached. So the image forming control device comes to bear an unnecessary load, which also raises the image forming control device cost. Additionally, while many variations are conceivable for the optional unit, it is very hard to cover them all since it is necessary to increase the capacity of the memory. While it is also conceivable to let the image information control device control the optional unit, the image information control device must process the image information to be printed at high speed. So there is a disadvantage of the image information processing time, which is important, becoming slow if the optional unit must be controlled in this fashion.
The first object of the invention, therefore, is to provide an image forming device to enable a rise of the essential printing operation speed of the image forming device. This is done by lessening the burden on the CPU of paper management for the image information control device and the image forming control device.
The second object of the invention is to provide an image forming device which enables to minimize the change in the image forming control device and the image information control device and to select their combination freely when optionally connecting the paper processing device, e.g., the paper feeding device and the paper ejecting device, to the image forming device.
The third object of the invention is to provide an image forming device which enables one to realize the fastest throughput with the paper conveyance control device determining the best printing timing according to the paper processing time of the optional unit, the paper conveying speed and paper conveying path length and the paper length and the printing mode of the image forming device and the optional unit by consistently and comprehensively managing the paper movement in the image forming device and the optional unit by providing a CPU dedicated to paper conveyance control.
The fourth object of the invention is to try to lower the interface circuit cost by connecting the image information control device and the random access memory by a serial transmission line by providing a shared random access memory between the image information control device and the paper conveyance control device.
To achieve the objects above, the invention, firstly, tries to raise the essential printing speed of the image forming device by dedicating the CUP of the image conveyance control device to dedicate CPU of the image information control device to image information control and the CPU of the image forming device to image formation so as to release them from the management of the paper processing device.
The invention, secondly, facilitates recombination by minimizing the change in the image forming device and the image information control device by performing control suitable for the combination of the paper processing device and the image forming device even if they are recombined with the paper processing device determining the difference in their models and specifications.
The invention, thirdly, enables one to realize the fastest throughput with the paper conveyance control device determining the best printing timing according to the paper processing time of the optional unit, the paper conveying speed and paper conveying path length of the image forming device and the optional unit and the paper length and the printing mode by consistently and comprehensively managing the paper movement in the image forming device and the optional unit by providing a CPU dedicated to paper conveyance control.
The invention, fourthly, enables one to reduce cost by decreasing the number of signal lines by connecting the image information control device and the random access memory by a serial transmission line.
Another object of the invention is to provide an image forming device which enables it to inform the user quickly of the status of the image forming device.
Another object of the invention is to provide an image forming device which enables it to use the memory efficiently by reducing the time for the image information control device to occupy the memory.
Still another object of the invention is to provide an image forming device which makes throughput of the whole image forming device the fastest with the paper conveyance control device determining status of the paper feeding device and selecting the best paper feeding source.
To achieve the objects above, the invention, again, tries to raise the essential printing operation speed of the image forming device by dedicating the CPU of image information control device to image information control and the CPU of the image forming device to image formation so as to release them from the management of the paper feeding and ejecting devices as well as minimizing the change in the image information control device and the image forming control device by meeting recombination of the paper feeding and ejecting devices, if any, just by exchanging a program of the paper conveyance control device.
The invention, also, provides print permission information to enable to obtain the fastest throughput from the paper conveyance control device by consistently and comprehensively managing the paper movement in the image forming device by providing a dedicated CPU in the paper conveyance control device and controls the image forming device optimally.
The invention, also, obtains the fastest throughput by providing in the paper conveyance control device a memory which shares information with the image information control device and with the image information control device receiving the schedule of the page to be printed and with the paper conveyance control device moving the paper in advance of the printing operation. It is possible to inform the user quickly of the status of the image forming device by grasping every movement of the paper which moves in the image forming device and writing it quickly in the shared memory and passing the paper movement to the host computer side via the image information control device.
The invention, in addition, makes the time for the image information control device to occupy the image memory the shortest by providing information to enable to erase the data kept in the image memory for the image information control device to re-output the image at the occurrence of a jam or other error when the paper conveyance control device, grasping the movement of the paper which moves in the image forming device quickly, acknowledges that paper has been ejected normally.
In particular, as the image forming device becomes multi-functional and as the number of paper feeding and ejecting ports increases, the time for each sheet of paper to remain in the device comes to differ. The sheets of paper are not ejected in their order of having been fed. While conventionally the image memory is cleared after all sheets of paper have been ejected, it is possible to use the memory more effectively if the image memory of the sheet of paper ejected earlier is cleared earlier. The invention enables memory clearing per page by providing a RAM release flag per page.
In the invention, also, the paper conveyance control device determines the status of the paper feeding device and selects the best paper feeding source as it knows the printing schedule beforehand and as it grasps the status of the paper feeding device quickly. For example, it selects another substitutable paper feeding source if the designated paper feeding source runs out of paper and a paper feeding source with a higher conveying speed if one is available.
Still another object of the invention is to provide an image forming device which can permit interruption if interruption print is requested while printing a series of jobs. The invention is available not only in a stacker having the job offsetting function but also in a stacker having a stapling function that is selectable job by job.
To achieve the object above, the invention is equipped with a dedicated control device to perform paper conveyance control. Such a paper conveyance control device is called the Paper Handling Controller (hereafter abbreviated as the xe2x80x9cPHCxe2x80x9d). The PHC is equipped with a random access memory to be shared with a image information control device.
The job schedule is written in that memory from the image information control device. The PHC, seeing the schedule in the memory, checks if there is interruption print or not. If there is, it counts its number of pages and checks if the number of interruption pages is storable or not. If it is, it requests the image information processing device to store the interruption page. The PHC executes the original job schedule while storing the interruption page. If the original job is a staple command, for example, it executes interruption print as soon as one time of the stapling process ends. In that case, it is possible to output the stapling processed printed matter and the interruption printed matter to the same ejection tray. If there are too many interruption pages, if it is impossible to store or if the interruption priority is high, meanwhile, the PHC requests to execute interruption print, halts the original job and makes the interruption printed matter be output to another tray than for the printed matter of the original job.